The invention relates to an appliance for preparing hot beverages, in particular coffee and espresso, which has a two-part brewing chamber that can hold or release a portion container.
The portion containers used in the known appliance are filter bags, so-called pouches, which, for the most part, have a flat, lens-shaped or pot-shaped design and consist of either filter paper or woven plastic material with coffee grounds sealed therein. The portion containers may also consist of deep-drawn aluminum or plastic foil drawn into the shape of a pot and provided with a lid.
For the purpose of preparing coffee, these portion containers, in particular the filter bags, are inserted into the two-part brewing chamber of the appliance composed of an upper chamber part and a lower chamber part. Following the insertion of the portion container, the brewing chamber is sealed pressure-tight and water-tight with the exception of a brewing-water intake line and a brew discharge line. During the brewing process, brewing water enters the brewing chamber under pressure and, if the filter bags are made from a filtering material, flows directly through the filter bags in the brewing chamber. In the brewing process, the brewing water leaches out the coffee grounds and flows in the form of the brewed beverage via the brew discharge line into a collection container. For the water-tight sealed portion container, additional means are provided in the brewing chamber which partially pierce or open up the container lid as well as the container bottom during the closing of the brewing chamber or during the brewing operation, either mechanically or through the pressure exerted by the brewing water.
The problem with the appliance is that when the brewing chamber is sealed with the portion container positioned therein, the brewing water may circumvent the portion container and leave the brewing chamber directly. The preferred result is that the brewing water flows completely, if possible, through the portion container, such that the total contents are leached out uniformly. It is assumed here that the portion containers, or the pouches and portion capsules, are provided with a circumferential collar, which, in the case of pouches, is an area where the upper portion and the lower portion are welded together, and for the portion capsules, is an area formed by a closing zone between the lid and pot. The collar of the portion capsules functions as a sealing surface between the upper portion and the lower portion of the brewing chamber. However, it has turned out that sealing the brewing chamber with a welded collar is not reliable in the case of pouches since the filter materials have a tendency to form folds after they are filled with the coffee grounds because of their insignificant deep-drawing capacity. This can result in an uneven collar structure when the upper and the lower parts are welded together and can lead to leakages in the brewing chamber during the brewing operation.
The known appliance is designed for use with pan-shaped filter bags that can also be considered as the pouches. The brewing chamber of the known appliance comprises a filter container as a lower part consisting of a pan-shaped inside space with a bottom that is lowered relative to the edge and a vertical, cylindrically closed, side wall that surrounds the edge (see German patent document DE 698 01 081 T2). A number of groove-shaped indentations are provided at the bottom, which extend in a radial direction toward a discharge opening. The lower part with inserted filter bag can be closed off with a flat lid as the upper part. The filter container with the lid forms the brewing chamber. In addition, the lid is provided with a sealing ring along its outer edge that moves radially outward under the pressure of the brewing water and fits itself against the vertical side wall of the filter container. The brewing water should flow through the filter bag from the top toward the bottom and out of the filter bag at those locations where the grooves are arranged. In contrast, only a small amount of brew should exit the filter bag in the areas between the grooves so that on the whole the brew does not flow too fast through the filter bag. In addition, the brewing water flowing into the filter container should not flow toward the outlet opening without first passing through the coffee grounds in the filter bag. For this, the bottom of the filter bag must be fitted directly over the bottom of the filter container area without grooves. The filter bag collar can be positioned below the sealing ring. Since this ring is arranged inside the brewing chamber, it is impossible to avoid that coffee particles are deposited in the area of the seal, thus resulting in leaks in the brewing chamber without careful cleaning.
The sealing ring of a known appliance is positioned inside the side wall of the filter container, and the filter container bottom can be provided with a larger number of cylindrical projections in place of the radial grooves. However, the sealing problem is still not solved. In both cases, it is possible that the brewing water does not completely penetrate the filter bag on the supply side, but flows past the filter bag. Additionally, the filter bag or the pouch must be inserted precisely into the pan-shaped inside space of the filter container and is difficult to remove following use.